PRB: Using a Self-Join to Produce a Cartesian Product

ID: Q45493

The information in this article applies to:

Microsoft SQL Server for OS/2, version 4.2
Microsoft SQL Server version 4.2

SYMPTOMS

In attempting to produce the Cartesian product of a table with itself, a self-join without a WHERE clause produces only the table itself.

CAUSE

A self-join without a WHERE clause does not produce a Cartesian product unless the two instances of the table are given aliases and the select list includes columns from both aliases. The following does not produce a Cartesian product:


   select * from t1,t1

WORKAROUND

The following does produce a Cartesian product:


   select x.c1,y.c1 from t1 x, t2 y

This is the intended operation of SQL Server.

Additional query words: Transact-SQL Windows NT


Keywords          : kbprg SSrvProg SSrvServer SSrvWinNT 
Version           : 4.2 | 4.2
Platform          : OS/2 WINDOWS 
Issue type        :

Last Reviewed: March 6, 1999